ESP32 Forum

Posted: **Thu Aug 22, 2019 9:18 am**

Is it possible to store data under struct like the one below in RTC memory so I can retain the values of all the objects on wake up

struct Button {
  const uint8_t PIN;
  volatile uint32_t numberKeyPresses;
  volatile bool pressed;
};

Posted: **Fri Aug 23, 2019 1:55 am**

Posted: **Fri Aug 23, 2019 10:26 am**

ESP_Sprite wrote: ↑
Fri Aug 23, 2019 1:55 am
Yes.

Thanks for the reply. What is the correct syntax for this. This is illegal

RTC_DATA_ATTR struct Button {
  const uint8_t PIN;
  volatile uint32_t numberKeyPresses;
  volatile bool pressed;
};

struct Button {
  RTC_DATA_ATTR const uint8_t PIN;
  RTC_DATA_ATTR volatile uint32_t numberKeyPresses;
  RTC_DATA_ATTR volatile bool pressed;
};

I am not quite familiar with attributes.

Posted: **Mon Aug 26, 2019 3:56 am**

Do it where you actually allocate memory for your data. Something like this (untested):

struct Button {
  const uint8_t PIN;
  volatile uint32_t numberKeyPresses;
  volatile bool pressed;
};

RTC_DATA_ATTR  struct Button my_button;

RTC_DATA_ATTR and struct